81 mercury 9.8

[bluethunder01071973]

i have many questions about this motor and the first one is about the compession. how to do it properly and also would like to know how fast should it go on the water with a 14foot john boat. also would like to know how can u tell if the water pump is properly working. and i have more but i need these answered first...one more. can this motor be jetted out to be a 15 horsepower

 

[WillyBWright]

Re: 81 mercury 9.8

Let's get the last one out of the way. No! That block was used in 6, 7.5, and 9.8Hp models. Never anything bigger. Also, simply changing a carb jet is more likely to get you less horsepower than more.

You might be able to plane a 14' Jon with just you in the boat. Low 20s planed, under 20mph not planed.

For a compression test, you'll need a tester with a hose. Both sparkplugs out, test each cylinder with five healthy yanks on the rope. Compression readings should be within 10% and hopefully in the 100psi ballpark